The invention relates to adhesive bonding and more particularly relates to removably bonding two parts together using adhesive. In its most immediate sense, the invention relates to separably adhesively bonding two parts together in such a manner that once the parts have been separated from each other, any remaining sections of the adhesive layer are so small that they can be easily removed.
In certain aerospace applications, parts are bonded together with adhesive and this can cause difficulty if one of the parts fails. For example, a heater blanket may be bonded to a metal vane using polysulfide rubber adhesive. If the blanket fails, it must be replaced. This is a labor- and time-intensive task because a) the adhesive is generally quite strong, b) the blanket may come apart when it is pulled off and c) the part may be of a shape which is not easily removed by peeling (e.g. the part may have a double curvature).
It has been proposed to provide in advance for easy separation between two such adhesively bonded parts. In accordance with this proposal, a serpentine pattern of flexible cable (for example, piano wire) is placed in the adhesive layer before the layer has cured and before the blanket is mounted to the vane. One end of the piano wire projects out of the adhesive. To separate the blanket from the vane, the wire is pulled out. When this happens, the wire cuts the adhesive and makes it possible to remove the blanket without pulling on the blanket itself. This reduces the breakup of the blanket during removal, and reduces the quantity of material remaining on the vane. This in turn makes the removal task easier.
This technique has not been entirely successful. This is because after the blanket has been separated from the vane, a regular pattern of large adhesive patches still remains on the vane. These patches are difficult to remove because they are so large.
It would be advantageous to separably adhesively bond two parts together in such a manner that any remaining adhesive can be easily removed after the parts have been separated.
One object of the invention is to provide a method and an adhesive structure which will separably adhesively bond two parts together in such a manner that after the parts have been separated, so little adhesive remains that it can be easily removed.
Another object of the invention is, in general, to improve on known methods and structures of this general type.
In accordance with the invention, the known proposal is modified by arranging the cable to have a particular pattern. This is a serpentine pattern having two opposed ends. The pattern has endpoints along those ends. The distance between adjacent unconnected endpoints is small with respect to the distance between adjacent connected endpoints, and the adjacent unconnected endpoints at one end of the pattern are located intermediate adjacent connected endpoints at the other end of the pattern.
In one preferred embodiment, the cable is arranged in generally straight line segments which bound acute angles. Advantageously, and in accordance with the preferred embodiment, the cable is made of several wires which are twisted together.